Combine ground meat, sliced beef, onion juice, oregano, thyme, chili flakes, black pepper, and salt.
Spread into a thin layer inside a plastic bag. Chill for at least 2 hours or overnight in the refrigerator for the flavors to meld.
Freeze until solid. Break or slice into thin strips.
When ready to serve, sauté in butter until browned and cooked through.
Heat olive oil in a saucepan. Add tomato paste and cook until slightly darkened.
Stir in passata and water. Bring to a boil.
Season with salt and a pinch of sugar. Simmer until thickened.
Broil the tomato and pepper until lightly charred.
Toast bread cubes at 300°F (150°C) until dry and crusty.
Melt 50 g butter until browned and foamy.
On a plate, layer bread cubes, spoon over tomato sauce, and top with doner meat.
Add more sauce, charred tomato and pepper, and a scoop of yogurt.
Finish with a dramatic pour of hot foaming butter.
